About the game
Sudoku Online is a number grid you complete with the digits 1 through 9. No digit may appear twice in the same line across, the same line down, or the same 3×3 block. A few squares hold starting numbers; the rest are yours to work out.
Work where the board is crowded. A square whose row, column and block already carry plenty of digits leaves few candidates, so the answer stands out. Notes mode keeps several candidates in one square until you cross them off. Beyond the four settings, X-Sudoku, Windoku, Killer and Kropki each add their own rule. Every grid has one answer, and logic finds it.
How to play
- Click a square and type a digit from 1 to 9.
- Keep each digit to a single appearance per row, per column and per 3×3 block.
- Turn on notes mode to store candidates in a square, then remove them as numbers land.
- In variant grids, respect the extra rule: diagonals, highlighted regions, target sums or dot markers.